Direct Air-cooled Steam Condenser Spray Cooling System Flow Condensation Heat Transfer Characteristics Research

The higher operating pressure of air cooled power plant greatly affects the safety and power output of steam turbine in summer, so the method of reducing air temperature by spray cooling is used. The key technologics and solution scheme of summer operation were approached in this paper.According to the low Reynolds number, the physical model regarding heat transfer and flow characteristic between fins are analyzed. Based on the model, the air-side heat transfer characteristics of the wavy finned flat tube are investigated in detail. The results indicated that the eddy region behind the tube lessen the heat transfer of tube fin. The parameters such as the air velocity and temperature, which affect the airside flow and heat transfer performance, are analyzed. A3D air flow field calculation is carried out, for the air-cooled condenser’s air fan and the A-shaped frame-work, in one power plant. The fin side of the condenser tubes is simplified by using a porous medium model. The distribution of velocity, temperature and pressure, within the air-cooled unit, is obtained. On the basis of the accurate physical models regarding flow and heat transfer characteristic between fins and air-condenser unit, using fins model detail calculation to obtain the temperature distribution of the whole finned tube by the bottom-up approach, and try to solve the multi-scale problems such as that ploblems in air-condenser system.The theoretical process of spray cooling is analyzed in this paper. The method of calculating the adiabatic saturated temperature by programming is given and the research shows that the adiabatic saturated temperature is the lowest temperature that makes the air saturated by spraying cooling system. Mathematic and Physical model of droplet evaporation is developed and solved. Droplet evaporation time in air condenser is analyzed with the model. The variation rule of the temperature and diameter of droplet with the ambient temperature and humidity is obtained.With couple algorithm and k-ε model, applying the heat and mass transfer theory for two-phase of air and water, numerical analysis model of spray cooling system is established. Influence of heat exchanging performance of the direct air cooling island by installing the spray cooling device has been researched and analyzed. Indeed the installation of spray cooling system in the direct air-cooling system can improve heat transfer and enhance the units economic and security. The results show that the important factors of influencing heat exchange are the size of the droplets and air contact area and the residence time of droplets in hot spots.